5 Common DUI Defenses Your Attorney May Use

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Facing DUI charges can be scary, leaving defendants to feel as though they have a rough road ahead. Fortunately, many procedures and tactics used to measure levels of intoxication can be challenged by a knowledgeable DUI lawyer. There are many defenses out there, but here are five of the more common DUI defenses your attorney may use to have your DUI dismissed.

Being Pulled Over Without Valid Reason

The Fourth Amendment protects you from illegal and unwarranted searches and seizures. It's also supposed to protect people from a stop-and-frisk or from being arbitrarily arrested without cause.

What this means is the police must have a valid reason for pulling you over in the first place. What constitutes a valid reason? Continually weaving in and out of lanes does, but crossing the yellow line one time without affecting oncoming traffic typically doesn't. Neither does being in a "bad" neighborhood. Driving through an area of high crime does not justify a pullover.

If you suspect you were pulled over without justification, your attorney can use this as a defense for the judge to drop the charges.

Feeling Forced to Take a Field Sobriety Test

In most jurisdictions, if you were told by the officer that you must complete a field sobriety test, or if you felt coerced in any way and that you had no alternative, the judge may rule that the sobriety test was involuntary. In this situation, the results of your sobriety roadside tests will be thrown out and not used as evidence in your case.

Non-Expert Administered Horizontal Gaze Nystagmus Test

Many times, an officer will shine a penlight in the suspect's eyes, looking for what's called horizontal gaze nystagmus (HGN). This is an involuntary back-and-forth movement or twitch of the eye that happens when you're intoxicated.

When the test is administered correctly by someone who's had HGN training, the evidence is pretty sound. In other words, there is a scientific basis for believing that this twitch occurs in those with a high BAC. But if the arresting officer was not properly trained, or if the following conditions were present when you were tested, the evidence may be thrown out in your case:

  • test was performed in an area with poor lighting
  • your eyes could not be clearly seen by the officer
  • oncoming headlights or the flashing lights of a police cruiser were in your line of vision while being checked for HGN

Sometimes, there are subtle things that could affect the results of the test. For instance, if you were wearing glasses, or if the light from the penlight was flickering, your attorney can present this as evidence that the test results are inaccurate.  

Results Swayed by Mouth Alcohol

After having several drinks, the lining of your mouth can still contain alcohol—more than what's in your blood. Therefore, it's highly possible that the presence of mouth alcohol can skew the results of the breathalyzer, resulting in a reading that does not accurately reflect your true BAC.

Every time you exhale, the alcohol in your blood becomes vaporized and leaves your lungs. Ideally, the breathalyzer is supposed to analyze the alcohol that comes from your lungs, but here's the thing: alcohol can stay in your mouth for up to 20 minutes after drinking, and the breathalyzer does not discriminate against the source of the alcohol. So if you've just left the bar when you were tested, it's possible your DUI lawyer will argue the evidence as inadmissible based on the "mouth alcohol" argument.

Breathalyzer Not Properly Maintained

Every state has laws regarding maintenance and calibration of a breathalyzer machine, and this includes the machines at police stations as well as inside mobile units.

A DUI lawyer from firms like Thomas & Associates, PC can ask for the maintenance logs of the machine to see if they were properly maintained at the correct intervals. If it can be shown that the breathalyzer wasn't calibrated often enough or that it has a history of giving inaccurate readings, the results from your test may be ruled inadmissible.